Tableau Tip: Make great looking band lines with area charts

When I was in Israel last week, we wanted to create a visualization that included band lines based on confidence intervals in the database. In other words, our table contained two measures: value and confidence interval.

Allen Smithee had created some interesting looking Bollinger Bands before, so I started there. I downloaded the workbook and noticed that while these look decent, they’re not perfect. This is the initial view:

Looks pretty good. But when you remove the lines for the upper and lower bands (or if you zoom in), you will see that the bands were made via reference bands for each discrete date, which makes them look like bars. I suspect the lines for the upper and lower were included to hide the rough edges of the bars.

Here’s how he created the reference lines:

I don’t think this looks polished enough, so I took an alternative approach: area charts.

I started by downloading some stock data from Google for various tech stocks for the past year. Next I created four calculations that I needed for Bollinger Bands.

Next I created a simple line chart across a continuous date dimension using the Moving Avg Close calculated field.

Now onto creating the bands. I want these to be an area chart on the secondary axis. I dragged the Bollinger Lower Band measure onto the secondary axis.

Then drop the Bollinger Band Width measure onto the secondary axis as well and synchronized the axis.

Next, right-click on the secondary axis and change the Mark Type to Area Chart.

All that’s left is a bit of formatting.

Remove the gridlines

Hide the header for the secondary axis

Change the color of the area chart sections: make the bottom section white and the top section gray

Change the color of the Moving Avg Close line to red

Move the primary axis to the front

Remove the column and row borders

I then repeated this exercise with a standard deviation calculation so you could see two types of bands. I suspect you agree that these look much more polished.

Steve, I don't know enough about Google Charts to answer your question. As an educational institution, you get Tableau for free if you want to use it in your class. This link has all of the details - http://www.tableausoftware.com/academic/students

This is the most helpful post I've been able to track down to create bands like this. I am hitting 2 problems though, and I'm wondering if you've got any suggestions. I need to plot 2 lines against the band: median performance, and my group's performance. It looks like Tableau only allows one line to be plotted at a time. The second issue is that my area chart has negative values. Tableau doesn't chart stacked area values correctly for negatives. All area chart values are on one side of the x-axis, so there is no way to show the values spanning both sides of the x-axis.

Thanks for any thoughts. I'm getting super frustrated with Tableau for anything other than simple charts. I had this chart done in five minutes in Excel and I'm on day 3 in Tableau... I'm hoping the learning curve gets faster.

Mike, you can plot as many lines as you want on the same axis by dropping the 2nd, 3rd, etc on top of the existing axis. This will then change the axis to the Measure Values field and will reveal the Measure Values shelf.

Andy - one question. The note above says that you can add multiple lines to the chart (i.e. show multiple lines within a band) but this doesn't seem to be working for me. I want to be able to display actual sales and planned sales within a 5yr high-low banding. Is it possible to do this?

Hi David. Depending on your method, you should be able to do it. If they are separate measures, then you put them on a combined axis. However, you would then need to make sure the banding part isn't also a combine axis because Tableau won't allow that. You would need to create some kind of calculation to make it work.